Class: RuboCop::Cop::Style::StringConcatenation

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Includes:
RangeHelp
Defined in:
lib/rubocop/cop/style/string_concatenation.rb

Overview

Checks for places where string concatenation can be replaced with string interpolation.

The cop can autocorrect simple cases but will skip autocorrecting more complex cases where the resulting code would be harder to read. In those cases, it might be useful to extract statements to local variables or methods which you can then interpolate in a string.

NOTE: When concatenation between two strings is broken over multiple lines, this cop does not register an offense; instead, ‘Style/LineEndConcatenation` will pick up the offense if enabled.

Two modes are supported:

  1. ‘aggressive` style checks and corrects all occurrences of `+` where

either the left or right side of ‘+` is a string literal.

  1. ‘conservative` style on the other hand, checks and corrects only if

left side (receiver of ‘+` method call) is a string literal. This is useful when the receiver is some expression that returns string like `Pathname` instead of a string literal.

Examples:

Mode: aggressive (default)

# bad
email_with_name = user.name + ' <' + user.email + '>'
Pathname.new('/') + 'test'

# good
email_with_name = "#{user.name} <#{user.email}>"
email_with_name = format('%s <%s>', user.name, user.email)
"#{Pathname.new('/')}test"

# accepted, line-end concatenation
name = 'First' +
  'Last'

Mode: conservative

# bad
'Hello' + user.name

# good
"Hello #{user.name}"
user.name + '!!'
Pathname.new('/') + 'test'

Constant Summary collapse

MSG = 
'Prefer string interpolation to string concatenation.'
RESTRICT_ON_SEND = 
%i[+].freeze

Instance Method Summary collapse

Methods included from AutoCorrector

support_autocorrect?

Instance Method Details

#on_new_investigation ⇒ Object 



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# File 'lib/rubocop/cop/style/string_concatenation.rb', line 68

def on_new_investigation
  @corrected_nodes = nil
end

#on_send(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/string_concatenation.rb', line 72

def on_send(node)
  return unless string_concatenation?(node)
  return if line_end_concatenation?(node)

  topmost_plus_node = find_topmost_plus_node(node)
  parts = collect_parts(topmost_plus_node)
  return if mode == :conservative && !parts.first.str_type?

  register_offense(topmost_plus_node, parts)
end

#string_concatenation?(node) ⇒ Object 



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# File 'lib/rubocop/cop/style/string_concatenation.rb', line 61

def_node_matcher :string_concatenation?, <<~PATTERN
  {
    (send str_type? :+ _)
    (send _ :+ str_type?)
  }
PATTERN